The invention relates to an arrangement for correcting registration in sheet guiding cylinders of a multi-color rotary sheet printing press in which sheets are transferred between individual printing units by transfer cylinders positively driven by gear drives and connected with respective printing cylinders of the individual printing units and also driven by gear drives.
The sheet guiding cylinders such as, i.e., transfer cylinders and printing cylinders are generally equipped with two diametrically opposite gripping elements. With these cylinders, the exactitude of operation of a rotary sheet printing press, in particular, maintaining of the registration when guiding the sheet and avoidance of doubling, is influenced by a quality of gear drives of sheet guiding cylinders. To provide for a precise exactitude of operation of a rotary sheet printing press, the sheet guiding cylinders and the drives should be manufactured with a high accuracy and that is connected with substantial expenses.
In multi-color printing presses, the position of a drive gear is changed by adjusting the gear of the drive relative to the middle point of a sheet guide cylinder and also relative the gripping element of the sheet guide cylinder, and a single deviation from a predetermined movement of one of the sheet guide cylinders requires adjusting of the drives of the entire press to minimize the error.
This method in multi-color printing presses results in high assembly costs and, besides, it may require dismounting of other structural units.
Another drawback of this method consists in that between the gear drive and a sheet guiding cylinder support, a wheel body need be mounted, and a correcting adjustment movement is provided for by a clearance between the wheel body and the sheet guiding cylinder. Providing such a body reduces the rigidity of mounting of the gear drive and of the entire gear train. Also, adjustment of the gear drive is necessary already during initial assembly of the press.
DE-OS 17 61 754 discloses providing in a gear drive, in the sheet transfer region, specially formed adjusting teeth to achieve an increased accuracy of sheet transfer. The drawback of this solution consists in that with time, because of teeth wear, the accuracy of transfer is reduced, and it is difficult to manufacture these teeth with a high accuracy.